JPH07192258A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a magnetic recording medium capable of increasing the film formation rate without impairing the film quality of the protective film. [Structure] After forming a magnetic layer made of a ferromagnetic metal thin film on a non-magnetic support, 40 to 700 kcal / (m · hr)
A protective film is formed by a magnetron sputtering method using a target material having a thermal conductivity of K). [Effect] Since the target material having high thermal conductivity can transmit the energy of incident ions to more target particles as lattice vibration, sputtering can be performed with less energy. Thereby, the sputtering rate is improved, the film formation rate is improved, and the productivity is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium in which a protective film is formed on a magnetic layer made of a ferromagnetic metal thin film by magnetron sputtering, and more particularly to a method for improving productivity.

[0002]

2. Description of the Related Art In the so-called ferromagnetic metal thin film type magnetic recording medium, a magnetic material made of metal or an alloy such as Co-Ni is plated or a vacuum thin film forming technique (vacuum deposition method, sputtering method, ion plating method, etc.). It is directly applied onto a base film such as a polyester film or a polyimide film. This ferromagnetic metal thin film type magnetic recording medium is not only excellent in coercive force, squareness ratio, etc. and excellent in electromagnetic conversion characteristics in the short wavelength region, but also can be thinned in the magnetic layer, so that recording demagnetization and reproduction are possible. There are various advantages such as a significantly small thickness loss at the time, and a high packing density of the magnetic material because it is not necessary to mix a binder or the like which is a non-magnetic material in the magnetic layer.

In this ferromagnetic metal thin film type magnetic recording medium, the magnetic layer is generally formed by a vacuum vapor deposition method. For example, a so-called oblique vapor deposition method in which a magnetic material is obliquely vapor-deposited on the surface of a base film is used. Proposed and put to practical use. In this case, a base film is wound around the outer peripheral surface of a cooling can rotatable in a predetermined direction, and the magnetic support is moved and run at a predetermined speed in accordance with the rotation of the cooling can while being vapor-deposited from a crucible. The magnetic material is incident on the surface of the base film from a direction forming an angle, and the magnetic material is vapor-deposited on the base film to form a magnetic layer.

By the way, when such a ferromagnetic metal thin film type magnetic recording medium is used in a digital video tape recorder or the like, the drum is rotated at a higher speed during recording / reproducing than in the case of being used in an analog video tape recorder or the like. Therefore, there is a problem that the magnetic recording medium is largely damaged by sliding with the magnetic head. So, from the past,
After a ferromagnetic metal thin film is formed on a base film, a protective film made of a carbon film, a SiO ₂ film or the like is formed on this ferromagnetic metal thin film, thereby attempting to ensure durability.

Various methods have been studied as a method for forming this protective film. However, for example, when the carbon protective film is formed by the vapor deposition method using an EB gun,
Since the carbon to be vapor-deposited is sublimable, only the portion exposed to the electron beam evaporates, and the film formation rate becomes unstable. Therefore, it is difficult to obtain a practical film.

On the other hand, the sputtering method has attracted attention because it can form alloy films of various metals having different vapor pressures. When this sputtering method is applied, for example, to the formation of a protective film on a metal magnetic thin film type magnetic recording medium, the durability and corrosion resistance of the magnetic recording medium can be improved.

Conventionally, the sputtering method is inferior in productivity to a film forming rate of about 1/10 to 1/100 as compared with the vapor deposition method, and thus lacks in productivity, and the apparatus becomes large in size for mass production. However, due to the development of a sputtering method such as a magnetron sputtering method or a facing target method, the film forming speed is currently increasing.

For example, in the magnetron sputtering method, since a magnet is arranged below the target and electrons are trapped by the leak magnetic field to sustain discharge (perform cyclotron motion), The target can be efficiently sputtered, and the film formation speed becomes relatively high. The film forming rate can be improved by increasing the number of targets arranged in the vacuum apparatus, increasing the amount of electric power supplied to each target, and the like.

[0009]

However, since the number of targets that can be arranged in a limited space is limited, it is difficult to increase the film formation rate by increasing the number of targets, and the supply to the targets is difficult. When the amount of applied electric power is increased, the heat generated during sputtering increases, so that the bonding agent such as solder that adheres the target and the backing plate begins to melt, causing a problem such as short-circuiting the electrodes.

As described above, it is the actual situation that a sufficient film formation rate cannot be obtained even by the magnetron sputtering method.

Therefore, the present invention has been proposed in view of the above-mentioned conventional circumstances, and it is possible to increase the film formation rate and improve the productivity without impairing the quality of the protective film. It is an object to provide a method for manufacturing a medium.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies as a means of achieving the above-mentioned object, and as a result, can increase the sputtering rate by efficiently transmitting the energy of incident ions to target particles. We thought that it was possible, and found that increasing the thermal conductivity of the target material is effective for this.

The method of manufacturing a magnetic recording medium according to the present invention comprises:
In the method for manufacturing a magnetic recording medium, which is proposed based on the above findings, in which a ferromagnetic metal thin film and a protective film are formed on a non-magnetic support, the protective film is 40 to 700 kc.
The film is formed by a magnetron sputtering method using a target material having a thermal conductivity of al / (m · hr · K).

That is, according to the present invention, by using a target material having high thermal conductivity, the energy of incident ions is transmitted to a larger number of target particles, the sputtering rate is improved, and the film formation rate is improved. Is. The relationship between the logarithm of thermal conductivity and the film formation rate is almost proportional, and it is possible to improve productivity by improving the thermal conductivity. The thermal conductivity is 40 kcal / (m · hr).
・ K) or more, more preferably 70 kcal / (m · hr)
・ K) or more. When it is less than 40 kcal / (m · hr · K), the effect of improving the film formation rate is low. on the other hand,
Carbon having a value of 700 kcal / (m · hr · K) or more is difficult to use from an industrial point of view because it is only diamond.

In the present invention, the ferromagnetic metal thin film serving as the magnetic layer is formed by the vacuum deposition method. As this vacuum deposition method, in addition to the usual vacuum deposition method, ionization and acceleration of the vapor flow are performed by electric field, magnetic field, electron beam irradiation, etc. to evaporate chemical species on the base film in an atmosphere with a large mean free process. Alternatively, a method of forming a magnetic thin film on the substrate may be used. In the present invention, after forming a ferromagnetic metal thin film by such a vacuum deposition method, a protective film is formed by magnetron sputtering.

As a method for forming the above-mentioned protective film, a so-called continuous winding method is employed in which the base film sent from the sending side is sputtered while sequentially running toward the winding side. In this continuous winding system, the base film on which the ferromagnetic metal thin film is formed is moved and supported while being supported by, for example, a large diameter can or the like arranged in the middle of the feeding side and the winding side, The target material arranged around the can causes the base film to be sputtered to form a protective film.

Examples of the protective film include SiO ₂ and Si
₃ N ₄ , SiN _x , BN, carbon, ZnO ₂ , Al ₂
O ₃ , MoS ₂ , SiC, etc. can all be used,
A carbon film is particularly suitable. The magnetic material forming the ferromagnetic metal thin film may be any of those generally used, but a metal magnetic material is preferably used. In this case, as the metal magnetic material, any of those usually used in this kind of magnetic recording medium can be used. To give a concrete example, Fe, C
Magnetic metals such as o and Ni, Fe-Co, Co-Ni, F
e-Co-Ni, Fe-Co-Cr, Co-Ni-C
r, Fe-Co-Ni-Cr, and the like.

As the non-magnetic support (base film), any of those usually used in this type of magnetic recording medium can be used. Specific examples include polyethylene terephthalate and polyethylene-
Examples thereof include polyester resins such as 2,6-naphthalate, aromatic polyamide films, and polyimide resin films.

Further, in the present invention, if necessary,
You may add the process of forming an undercoat film on the said base film, the process of forming a backcoat layer, a topcoat layer, etc. In this case, the film forming conditions for the undercoat film, the back coat layer, the top coat layer, and the like are not particularly limited as long as they are the methods usually applied to the method for manufacturing a magnetic recording medium of this type.

[0020]

When the present invention is applied and a protective film is formed by magnetron sputtering, if a target material having a high thermal conductivity is used, the film forming speed is improved.
It is considered that the reason is as follows. The target material having high thermal conductivity makes it easy to transmit the energy of incident ions to more target particles as lattice vibration. Therefore, the energy due to the lattice vibration near the sputtered particles becomes large, and the sputtering can be performed with less energy. This makes it possible to improve the sputtering rate, the film forming rate, and the productivity.

[0021]

EXAMPLES A method of manufacturing a magnetic recording medium according to the present invention will be specifically described below based on experimental results. First,
The configuration of the magnetron sputtering apparatus used in the protective film forming step of the magnetic tape manufactured by applying the present invention will be described.

In this device, as shown in FIG.
A feed roll 3 that rotates at a constant speed in the counterclockwise direction in the drawing at the upper side in the vacuum chamber 1 in which the inside is made a vacuum state by being exhausted from exhaust ports 11 provided at the head and the bottom, respectively. And a winding roll 4 which rotates at a constant speed in the clockwise direction, the base film 2 on which the magnetic layer is formed is sequentially run from the feed roll 3 toward the winding roll 4.

A cooling can 7 having a diameter larger than the diameters of the feed roll 3 and the take-up roll 4 is provided in the middle of the movement of the base film 2 from the feed roll 3 to the take-up roll 4. Is provided. The cooling can 7 is arranged so as to pull out the base film 2 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing. The feed roll 3, the take-up roll 4, and the cooling can 7 each have a cylindrical shape having a length substantially the same as the width of the base film 2.
A cooling device (not shown) is provided inside the cooling can 7 so as to prevent the base film 2 from being deformed by heat during sputtering.

Therefore, the base film 2 is sequentially fed from the feed roll 3, passes through the peripheral surface of the cooling can 7, and is wound up by the winding roll 4. Guide rolls 5 and 6 are provided between the feed roll 3 and the cooling can 7 and between the cooling can 7 and the take-up roll 4, respectively. A predetermined tension is applied to the base film 2 traveling from the cooling can 7 to the winding roll 4 so that smooth movement traveling can be performed.

On the other hand, in the vacuum chamber 1, a target material 9 made of carbon is arranged below the cooling can 7, and the target material 9 is attached to a cathode electrode 8 made of Cu. Then, by applying a predetermined cathode input power to the cathode electrode 8, a discharge occurs between the target material 9 and the cooling can 7,
The carbon blown out from the target material 9 adheres to the base film 2 traveling on the peripheral surface of the cooling can 7 to form a protective film.

A magnet (not shown) is provided below the cathode electrode 8 so that a magnetic field exists on the upper surface of the cathode electrode 8 due to the leakage magnetic field of the magnet. When the sputtering is performed in the presence of such a magnetic field, electrons are trapped by the leakage magnetic field to sustain the discharge, so that the target material 9 can be efficiently sputtered.

Then, in the vicinity of the cooling can 7, a position close to the feed roll 3 and a position close to the take-up roll 4 along the peripheral surface of the cooling can 7 are adhered plates 10a and 10b.
Are respectively arranged. As a result, these adhesion-preventing plates 10
Sputtering is performed only on the surface of the base film 2 exposed from a and 10b, and the protective film material other than the amount deposited on the surface of the base film 2 is
The adhesion-preventing plates 10a and 10b are attached to the adhesion-preventing plates 10a and 10b.
It is held by a and 10b. Therefore, there is no possibility that the protective film material attached to other than the surface of the base film 2 will fall off on the target and cause abnormal discharge, and the quality of the protective film obtained can be stabilized.

It is desirable that the deposition-preventing plates 10a and 10b are kept at a predetermined temperature in order to enhance the adhesiveness with the protective film material attached to the deposition-preventing plates 10a and 10b. A partition plate 12 is provided in the vacuum chamber 1 so as to divide the cooling can 7 into a lower side and an upper side. As a result, the sputtering gas does not diffuse to the upper side in the vacuum chamber 1 partitioned by the partition plate 12, so that the sputtering efficiency is improved.

Hereinafter, a method of forming a protective film by using the above magnetron sputtering apparatus and manufacturing a magnetic tape will be described. First, a base film having an undercoat film formed on its surface was produced. That is, latex particles containing acrylate as a main component (average particle size 30 nm)
Was coated on the surface of a polyester film having a thickness of 10 μm so that the density of the latex particles would be 10 million particles / mm ² to obtain the base film.

Next, a magnetic material (Co ₈₀ Ni ₂₀
Alloy: Numerical value represents% by weight. ) Is filled and the magnetic material is evaporated by an electron gun in a vacuum chamber maintained at a predetermined vacuum degree, and the base film is moved and run at a predetermined speed along the peripheral surface of the cooling can. The above magnetic material was obliquely incident on the surface of the film to form a magnetic layer. During this oblique vapor deposition, oxygen gas was introduced into the surface of the base film at a rate of 300 cc / min, and the incidence of the magnetic material on the surface of the base film was set to be in the range of 40 to 90 °. The feed rate of the base film was set so that the thickness of the obtained magnetic layer was 200 nm.

Then, a back coat layer made of urethane resin and carbon was applied to the surface opposite to the surface on which the magnetic layer was formed.

Subsequently, a carbon protective film was formed on the magnetic layer by using the magnetron sputtering apparatus shown in FIG. At this time, the degree of vacuum in the vacuum chamber is set to 2 Pa and Ar
Magnetron sputtering was performed in a gas atmosphere while controlling the feeding speed of the magnetic tape so that the total thickness of the protective film was 200 nm. As the target material, five types of materials having different thermal conductivities were used. As these target materials, width 200 mm x length 150 m
The distance from the base film is 5
It was set so as to be 0 mm.

Further, a perfluoropolyether was top-coated on this protective film and then cut into a width of 8 mm to obtain sample tapes of Examples 1 to 3 and Comparative Examples 1 and 2.

Each sample tape obtained as described above was manufactured by Sony Corporation under the trade name BS3000.
The still characteristics and shuttle characteristics were examined by a modified machine. The still characteristic was evaluated by the number of passes until the output deteriorated by 3 dB from the initial value, and the shuttle characteristic was evaluated by the output attenuation amount from the initial value after the tape was run 100 times for 30 minutes. Further, for each sample tape, the film thickness (dynamic rate) of the protective film formed at the film forming speed of 1 m / min was also examined.

The results are shown in Table 1 together with the thermal conductivity of the target material used.

[0036]

[Table 1]

From Table 1, as in the sample tapes of Examples 1 to 3, the thermal conductivity is 40 kcal / (m · hr · K).
It can be seen that the use of the above target materials can increase the dynamic rate of forming the protective film and improve the film forming rate. Further, by using the target material having high thermal conductivity, the still characteristics and shuttle characteristics of the sample tape are not particularly deteriorated.

FIG. 2 shows the relationship between the thermal conductivity of the target material and the dynamic rate of forming the protective film. From Fig. 2, the logarithm of the thermal conductivity of the target material and the dynamic rate show a proportional relationship, and the higher the thermal conductivity of the target material, the faster the base feed rate during the formation of the protective film can be. I understand. That is, it is possible to improve the sputtering rate, the film formation rate, and the productivity.

Although the method for manufacturing the magnetic recording medium according to the present invention has been described above, the present invention is not limited to the above. For example, the materials and forming methods of the base film, the ferromagnetic metal thin film, the protective film, the undercoat film, and the back coat, which form the magnetic recording medium, can be appropriately modified and changed without departing from the scope of the present invention.

[0040]

As is clear from the above description, when the present invention is applied and a protective film is formed by sputtering using a target material having a high thermal conductivity, the film formation rate is improved. The productivity can be improved without impairing the quality of the protective film.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a sputtering apparatus used for forming a protective film in a method of manufacturing a magnetic recording medium according to the present invention.

[Fig. 2] Thermal conductivity and dynamic ray of target material
It is a characteristic view showing the relationship with the.

[Explanation of symbols]

 1 ... Vacuum chamber 2 ... Base film 3 ... Feed roll 4 ... Winding roll 7 ... Cooling can 8 ... Cathode electrode 9 ... Target 10 ... Adhesion prevention plate 11・ ・ ・ Exhaust port 12 ・ ・ ・ Partition plate

Claims (1)

[Claims] 1. A method of manufacturing a magnetic recording medium, comprising forming a ferromagnetic metal thin film and a protective film on a non-magnetic support, wherein the protective film is 40 to 700 kcal / (m · hr ·
A method of manufacturing a magnetic recording medium, which comprises forming a film by a magnetron sputtering method using a target material having a thermal conductivity of K).